Sound record



- sound-tracks are impressed and/or from whose Patented Apr. 16, 1935UNITED STATES SOUND RECORD Boletech c. Bren, Cedar Grove, N. 1.,

Dupont Viscoloid Company, Wilmlngt a corporation of Delaware assignor toon, DeL,

No Drawing. Application March 29, 1934,

Serial No. 717,953

11 Claims.

This invention relates to sound records such as films, tablets, discs,or other bodies upon which surface sound tracks are reproduced, andrelates 5 more particularly to the use of thermoplastic resins obtainedby the polymerization of acrylic acid, alkacrylic acid, theirpolymerizable derivatives and homologues, in manufacture of such soundrecords.

Sound records and other types of sound repro-' ducing surfaces, asusually made from waxes, resins, or mixtures oi these and othermaterials, often show certain disadvantages. phonograph records, forexample, some of the more important include brittleness and backgroundnoise, the inability to flow freely under a moderate pressure, to setrapidly, to come away cleanly from the master andgive a smooth polishedarticle relatively free from air bubbles.

An object of the present invention is to provide a simple and economicalmethod of making sound records of improved quality. A further object isto provide a sound record, the portion or which, carries the soundtracks being substantially tree of the above mentioned deficiencies inheretofore known sound records. A further object isto provide a soundrecord in which the playing surface at least is water insoluble,non-hygroscopic, tough, flexible, durable, and yet capable ofreproducing sound with extraordinary fidelity. Other objects or theinvention willbe apparent from the description given hereinafter.

The above objects are accomplished according to the present invention bymaking at least that portion or a sound record in which the sound tracksare impressed, if not the whole record, of a composition comprising athermoplastic resin obtained from the derivatives or homologues ofacrylic acid or alkacrylic acid; particularly the nltriles, amides,substituted alkyland aryl amides; and more specifically the esters ofthe alkacrylates such as the alkyl esters of methacrylic acid, forexample, methyl methacrylate, ethyl methacrylate, and the allryl estersof ethacrylic acid, as for example, methyl ethacrylate and ethylethacrylate, and the higher alkyl esters of the higher alkyl acrylates.Of the alkacrylio acid esters it is preferred to use methylmethacrylate, the polymer of which is unusually well adapted for thepreparation of sound records. Inter polymers or mixtures of polymers ofthe compounds may be used if desired. The resins may either be usedalone or combined with plasticizers, filling or coloring materials, andthe like, depending inter alia upon the particular use and in, thecopending application In the case of carnauba,

effect desired, as will be more fully understood by those skilled in theart to which this invention particularly appertains.

The above compounds may be prepared by any suitable process, thealkacrylates for example may 5 be prepared in accord with the processdescribed oi Rowland Hill, Serial No. 641,113, filed November 3, 1932,granted November 13, 1934:, as U. S. Patent 1,980,483.

It is generally desirable to fabricate the record-- ing surface byeither first forming a record blank from the polymerized resin andsubsequently impressing the sound-track into the blank in a separateoperation or simultaneously forming the record with the sound track in asingle operation. The latter operation can be readily conductedbyintroducing the resin in the press as a powder or as a preform. Anyother suitable mode or operation may be employed.

The polymers and particularly the methyl 2c methacrylate polymer,.whichit is preferred to employ, are thermoplastic resins which have thevaluable property or setting from a plastic moldable condition into arigid or semi-rigid solid, the rigidity of which is determined, interalia, by the particular resin and/ or the type and amount of othersubstances present. The resin, with or without filling, plasticizing, orother addition agents, may be molded by any suitable process such asthose described above. Sound records prepared in accord with thisinvention have the ability to reproduce with absolute fidelity thetexture of the molding surface and the finished record comes away fromthat surface cleanly, giving a tough, durable record exceptionally freefrom background noise. These resins are, therefore, surprisingly welladapted for the preparation of such products. The resins may likewise befabricated into the softer type records which are used to receive thesound track directly from 4.0 a vibrating stylus.

With these products may be incorporated waxes or resins, or both, aswell as filling materials. In addition in some cases plasticizing agentsmay be advantageously used, such for example, as 4.5 triacetin,champhor, the alkyl phthalates, or any of the plasticizing and/oraddition agents re= ferred to in the above cited application. Suitablewaxes may be incorporated with the alkacrylates and/or their polymers,such as hard parafiin, ceresin, ozocerite, Montan, candelilla, shellac,Japan wax, and the like. Stearic acid may also be added as well as thestearate soaps, including those of sodium, zinc, lead, aluminum, andother metals. Aluminum and calcium palmitate may be used, as well asalso the various resinates. Natural resins, such as the copals, shellac,pontianak, rosin, dammar, sandarac, etc., may be employed, as well asthe synthetic resins, such as phenol-formaldehyde, urea-formaldehyde,etc., pitches, such as stearic pitch, or petroleum or gas tars aresometimes useful. Filling materials, such as graphite, talc, clay,diatomaceous earth, and the like, may be used with or without fibrousfillers as asbestos, cellulose, cotton fioc, wood powder, and the like.

Due primarily to the relatively high tensile strength andnon-shatterable nature of records made from the esters of thealkacrylates, it is not generally necessary to make the record as thickas those now in use. Moreover, inasmuch as the walls are uniformly hardand homogeneous throughout, and the material is substantially unaffectedby water or moderate heat, the tendency to warp, crack, or peel, isreduced to a minimum.

The outstanding advantages inherent in these thermoplastic resins is intheir ability to provide an excellent surface in which to impress apermanent, durable sound track. It is, accordingly, of

'advantage, in some instances, especially if an inflexible record isdesired, to utilize the resin as a surface supported on a more or lessfirm base such as are often used in this art; cardboard, light metalalloys, pitch compositions, and similar bases may, if desired, beemployed. The resin may, of course,.be placed on one or both sides ofthe record to permit the preparation of single or double faced records.

In the manufacture from the preferred ester as a base or surface uponwhich sound records may be impressed, there is first prepared, forexample, a composition containing polymerized methyl methacrylate, 9%triacetin, and 1% ethyl palmitate. The mixture is placed in a discshaped mold, preferably already hot, conforming with the shape of therecord desired and fitted with matrices. The mold is then closed and thematerial heated and pressed. A suitable temperature is irom-180 C., anda pressure of from approximately 2000 to 4500 pounds per square inch andup is applied for a short period, usually about two minutes. The recordis then cooled and withdrawn from the press. It will be found to havefaithfully reproduced both visually and orally the impression of themaster.

Other compositions adapted for making soundrecording surfaces in amanner analogous to that described, are:

Example 1 Per cent Polymerized methyl methacrylate 99 Ethyl palmitate 1Example 2 Per cent Polymerized methyl methacrylate 90 Diamyl phthalate 9Stearic acid 1 Example 3 Per cent Polymerized methyl methacrylate 87.0Dibutyl phthalate 12.5 Stearic acid 0.5 Example 4 Per cent Polymerizedmethyl methacrylate 60 Diamyl phthalate 10 Diatomaceous earth 29 Stearicacid 1 It will be understood that the examples given above in no waylimit the invention, for various compositions which are suitable for thepreparation of sound records not illustrated thereby can readily bemade. Moreover, it is not essential to the present invention that theabove steps of forming the record be carried out, for a great many ofthe methods now employed in the molding of thermoplastic materials maybe utilized with equally good results. If desired, the unsaturatedpolymerizable compound may be polymerized in situ in the mold.

Various plasticizers, such as those described in the examples, as wellas those given in the Hill disclosure, are employed primarily to lowerthe molding temperature of the material to a convenient point, thegreater the proportion of the plasticized present in the composition thelower will be its molding temperature. The above designated waxes areemployed usually to aid in preventing the finished molded record, due toaddition agents present or other causes, from adhering to the mold andin this capacity they act somewhat as a lubricant.

In some adaptations of the present invention the polymerization product,with or without plasticizer, may be used as a firm, more or lessyielding surface which is backed by a hard, unyielding support layer.The resin veneer makes it possible to provide a tough, durable recordhaving substantially no ground noises while the base provides anunyielding support therefor. I

From a construction of the above disclosure, it will be appreciated thatany sound record consisting wholly or in part of a thermoplastic resinprepared from acrylic acid, alkacrylic acid, or their homologues orderivatives, with or without plasticizers and/or addition agents, willcome within the scope of this invention without sacrificing any of itsadvantages.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

I claim: 7

1. A sound record having a sound track impressed therein, the portion ofsaid record containing the sound track being made of a compositioncomprising a thermoplastic resin from the group consisting ofpolymerized acrylic acid, alkacrylic acid, and their esters, nitriles,amides, alkyl substituted amides and aryl substituted amides.

2. A sound record having a sound track impressed therein, the portion ofsaid record containing the sound track being made of a compositioncomprising a thermoplastic resin from the group consisting ofpolymerized acrylic acid, alkacrylic acid, and their esters, nitriles,amides, alkyl substituted amides and aryl' substituted amides, and aplasticizer.

3. A sound record having a sound track impressed therein, the portion ofsaid record containing the sound track being made of a compositioncomprising a polymerized allgvl ester of an alkacrylate.

4. A sound record having a sound track impressed therein, the portion ofsaid record containing the sound track being made of a compositioncomprising a polymerized alkyl ester of an alkacrylate, and aplasticizer.

5. A sound record having a sound track impressed therein, the portion ofsaid record containingthe soundtrackbeingmadeoiacomposition comprising apolymerized alkyl ester of an alkacrylate, a plasticizer, and a fillingmaterial. 6. A sound record having a sound track impressed therein, theportion or said record containing the sound track being made 0! acmnposition comprising polymerized methyl methacryiate.

7. A sound record having a sound track impressed therein, the portion oisaid record containing the sound track being made of a compositioncomprising polymerized methyl methacrylate, and a plasticizer.

8. A sound recordhaving a sound track impressed therein, the portion ofsaid record containing the sound track being made of a compositioncomprising polymerized methyl methacrylate, a plasticizer, and a tiller.

9. A sound record having a sound track impressed therein, the portion oisaid record contaming the sound track being made oi a compositioncomprising approximately 90% methyl metghacrylate, 9% triacetin, and 1%ethyl palmita 10. A sound record comprising a surface made of acomposition comprising a thermoplastic resin from the group consistingof polymerized acrylic acid, alkacrylic acid, and their esters,nitriies, amides, alkyl substituted amides, and aryl substituted amides,and a backing comprising a hard, unyielding base.

ll. A sound record comprising a yielding surface veneer made of acomposition comprising a thermoplastic resin from the group consistingof polymerized acrylic acid, alkacrylic acid, and their esters,nltriles, amides, alkyl substituted amides, and aryl substituted amides,and a plasticizer, and a backing comprising a hard, unyield- BOZETECH C.BREN-

